In the manufacture of mineral wool, up to 30% of the mineral-wool mass taken from the furnace is scrapped as waste. Waste also occurs from the spinning machine, from the skiving or side-cutting of mineral wool into blocks, from faulty conditions during the manufacture of the mineral-wool mass, and in the transportation of the mineral-wool mass to or within the spinning machine. Mineral-wool waste may also constitute material which has been scrapped after use, for example mineral wool that has been used for plant cultivation purposes in the absence of soil, this material being considered unsuitable for further use at the end of the cultivating season and consequently being returned to the manufacturer for destruction.
One method of destructing and, at the same time, utilizing such mineral-wool waste or scrap is to press the mineral wool into briquette form, while admixing the scrap with additives, such as cement for instance, for the purpose of increasing the mechanical strength of the briquettes. These briquettes are charged to the furnace together with a conventional starting material, diabase and coke. This method is cost demanding, due to the necessity of compressing the mineral wool and admixing metered quantities of additives therewith. Since some of the briquettes do not have mechanical strength sufficient to withstand the stresses to which they are subjected such briquettes will be crushed in the furnace and therewith prevent hot furnace gases from flowing upwards in the furnace to preheat the furnace charge and exit from the furnace.
Another method, described in WO 87/07591, is to introduce the mineral-wool scrap into the furnace with the aid of a burner. In this case, the scrap is introduced into the furnace together with a fuel or with a gas needed for combustion, for example air or oxygen, depending on the burner construction. The drawback of this method resides in the difficulty encountered in controlling the furnace temperature, and the temperature of the resultant melt is particularly liable to vary with time. When the power generated by the burner is too low in relation to the amount of waste introduced through the burner, non-melted scrap material is likely to block the path of the exiting furnace gases which flow through the furnace to the furnace outlet.
An object of the present invention is to avoid the above drawbacks associated with known techniques, and to provide a method by means of which mineral-wool scrap can be destructed in a controlled fashion without negative influence on the operating conditions of the furnace used to produce the mineral-wool melt.
Another object of this invention is to utilize the destructed waste in the manufacture of mineral wool.
A further object is to provide apparatus operative to convert mineral-wool scrap to a molten form for the manufacture of mineral wool.
Thus, the present invention relates to a method of destructing mineral-wool scrap and re-using the scrap in the manufacture of mineral wool, by producing in a furnace a melt intended for use in the manufacture of mineral-wool. The method includes the steps of introducing finely-divided mineral-wool scrap into a container and causing the finely-divided scrap to pass through a heating zone generated in the container by an oxygen burner and in which the mineral-wool scrap is converted to a molten state; and passing the molten mineral-wool scrap to a molten bath generated in a furnace for use in the manufacture of mineral wool, or to an intermediate container located between the furnace and a spinning machine, by passing the melt from the furnace to the intermediate container. The present invention also relates to an apparatus for destructing mineral-wool scrap and reusing the scrap for the manufacture of mineral wool, by producing in a furnace a melt intended for use in the manufacture of mineral-wool, the apparatus including a container, at least one oxygen burner mounted in the container wall and operative to bring the mineral-wool scrap to a molten state, and at least one conduit for removing molten mineral-wool scrap, the conduit connecting the container to the furnace or to an intermediate container arranged between the furnace and a spinning machine.
The present invention will now be described in more detail with reference to the accompanying drawing, in which